The compressed air stream generated by a compressor typically will include moisture, oil, particulates and other contaminants. To remove such contaminants, compressed air systems commonly are provided with filters, condensate traps, and similar air stream cleansing apparatus. Of course, because they capture and accumulate contaminants, periodic servicing is required to maintain the air cleansing apparatus in proper working order. In the case of filters, the filter element gradually loads with the contaminants, particulates for example, and periodic filter element servicing, either by cleaning or replacement, is required.
Air filters represent a cost of production of useable compressed air, the required periodic cleaning or replacement of the filter element being one element of such cost. In addition, however, a pressure drop occurs as the air stream passes through the filter, and the useable air pressure downstream of the filter is reduced accordingly. The cost of this pressure drop, in terms of the cost of power for the incremental compressor operation required to produce a minimum useable pressure downstream of the filter, is another cost element of compressed air production. Moreover, since the pressure drop across the filter will increase with increased filter loading, the cost of power for driving the compressed air through the filter increases as the filter loads.
The task of optimizing a compressed air system to operate satisfactorily at minimum cost includes minimizing filter operating cost. Optimization techniques for this purpose are known, for example such as disclosed on Page 2 of Ultrafilter News, January 1997, and related documents of Ultrafilter International. U.S. patents disclosing filters and filter housings or casings include U.S. Pat. No. Des. 255,045. U.S. Pat. No. Des. 297,349, 4,157,968 and U.S. Pat. No. 4.172,798. U.S. patents disclosing differential pressure detection as by gauges and the like include U.S. Pat. Nos. 4,030,365, 4,347,744, 4,385,525, 4,559,834, 4,838,090, 4,890,497, 5,061,832, 5,183,983 and 5,373,746.
The present invention relates to a novel and improved apparatus for optimizing compressed air filter operation by minimizing filter operating cost. The invention includes an electronic monitoring apparatus which monitors filter operation. Based on repetitive detection of the pressure drop across the filter and other parameters, including several programmed into the apparatus by the user, the apparatus indicates when filter element renewal is required. The apparatus can indicate required filter element replacement on any of several criteria, including a maximum time period of filter use, a maximum differential pressure across the filter, and a cost optimization technique which relies on comparison of filter operating cost with filter replacement or renewal cost. More specifically, the logic of the novel filter monitor assesses the tradeoff between filter element replacement or renewal cost and the escalating cost of the pressure drop across the filter as the contaminant loading in the filter increases through use.
The apparatus is self-contained, including its power source and all necessary programming options and displays, and is configured to be carried directly by the filter housing through connection to a conventional pressure gauge connection on the filter housing.
It is therefore one object of the invention to provide a novel compressed air filter monitoring apparatus.
Another object of the invention is to provide a compressed air filter monitor with integral programming capability.
A further object of the invention is to provide a compressed air filter monitor with a novel filter operating cost optimization scheme.